Dr Who assistants assistence required!

[redexpat]

Hi everyone
I am based in Denmark. I suggested DH watch Dr Who on iplayer. He is now hooked, but keeps asking questions that I just dont know the answers to - mainly because I've been living here so havent seen it for years.

From Billie Piper to Catherine Tate - Catherine Tate asks Billie to look out for a woman and point her to a particular bin. Billie then fades into thin air. Please explain!

Also how do we get from Catherine Tate to the beautiful Scottish redhead?

I have googled, but can't find the answers. TIA

spoilers!

Rose was dispatched to an alternative universe with NO WAY of coming back EVER....but managed to becasue universe in danger yada yada.

Donna (catherine Tate) melded with doctor's chopped off hand convieniently kept in Jar in Tardis to become doctor/donna meld, which was too much for her puny human brain to stand, or it would melt - so the doctor sucked out her memories (I cried at this bit..)

Donna buggers off, doctor travels alone for a bit. regenerates, falls into garden of approx 9 year old little girl, promises to be back in ten minutes when he's sorted out some tardis stuff, pops back 15 years later and she has grown into beautiful scottish red-head. who marries Rory.

don't let's start on River Song.

Thank you! DH and I are much obliged!